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    Influencia del ph sobre el efecto tĂłxico inducido en clones de Dictyosphaerium Chlorelloides sensibles y resistentes a Cromo (VI)

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    El presente estudio establece una correlaciĂłn entre las variaciones de pH en el medio y las concentraciones de Cromo (VI), mediante su efecto en poblaciones de Dictyosphaerium chlorelloides, microalgas eucariotas cosmopolitas de agua continental. Se cultivaron en medio BG11 dos clones de D. chlorelloides, uno sensible al Cr (VI) y otro resistente a concentraciones de 25 μg/ml, en un rango de pH entre 2,5 y 11 para determinar el efecto de la acidez. Habiendo establecido un rango de pH definitivo (3-7,5), realizamos los ensayos de toxicidad para obtener el valor de pH mĂ­nimo al que la poblaciĂłn de microalgas no sufrĂ­a variaciones estadĂ­sticamente significativas. El análisis de la exposiciĂłn a Cr (VI) evidenciĂł una NOEC ajustada al valor de pH=4,25 para ambos clones. Los valores de CI50(72) obtenidos a pH 7,5 y 4,25 evidenciaron variaciones estadĂ­sticamente significativas entre ambos valores de pH, no habiendo diferencias significativas relativas al crecimiento poblacional en la cepa sensible de D. chlorelloides, aunque sĂ­ en el clon resistente.This paper explains the relationship between the environmental variations of pH and Chromium (VI) concentration, by their effect on populations of Dictyosphaerium chlorelloides, eukaryotic cosmopolitan microalgae of fresh water ecosystems. Two strains of D. chlorelloides were cultured in BG11 culture medium, being one of them sensitive to Cr (VI) and the other one resistant up to concentrations of 25 μg/ml, at pH values between 2.5 and 11 in order to determine their viability. When the pH range was determined (3-7.5), toxicity assays were done to obtain the minimum value of pH in which the microalgal populations did not vary significantly. The analysis of Cr (VI) exposure demonstrated a NOEC fitted to the pH value of 4.25. The IC50(72) values obtained at pH 7.5 and 4.25 showed significant statistic variations between both pH values, and there were not significant differences related to community growth in the sensitive strain, unlike the resistant one
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